Fix build with Bison 3.7

https://bugs.gentoo.org/736499

Patch copied from upstream source repository:

https://github.com/qtwebkit/qtwebkit/commit/d92b11fea65364fefa700249bd3340e0cd4c5b31

From d92b11fea65364fefa700249bd3340e0cd4c5b31 Mon Sep 17 00:00:00 2001
From: Dmitry Shachnev <mitya57@gmail.com>
Date: Tue, 4 Aug 2020 21:04:06 +0300
Subject: [PATCH] Let Bison generate the header directly, to fix build with
 Bison 3.7

Starting with Bison 3.7, the generated C++ file #include's the header
by default, instead of duplicating it. So we should not delete it.

Remove the code to add #ifdef guards to the header, since Bison adds
them itself since version 2.6.3.
---
 Source/WebCore/css/makegrammar.pl | 21 +--------------------
 1 file changed, 1 insertion(+), 20 deletions(-)

diff --git a/Source/WebCore/css/makegrammar.pl b/Source/WebCore/css/makegrammar.pl
index 5d63b08102eb5..9435701c70612 100644
--- a/Source/WebCore/css/makegrammar.pl
+++ b/Source/WebCore/css/makegrammar.pl
@@ -73,25 +73,6 @@
 }
 
 my $fileBase = File::Spec->join($outputDir, $filename);
-my @bisonCommand = ($bison, "-d", "-p", $symbolsPrefix, $grammarFilePath, "-o", "$fileBase.cpp");
+my @bisonCommand = ($bison, "--defines=$fileBase.h", "-p", $symbolsPrefix, $grammarFilePath, "-o", "$fileBase.cpp");
 push @bisonCommand, "--no-lines" if $^O eq "MSWin32"; # Work around bug in bison >= 3.0 on Windows where it puts backslashes into #line directives.
 system(@bisonCommand) == 0 or die;
-
-open HEADER, ">$fileBase.h" or die;
-print HEADER << "EOF";
-#ifndef CSSGRAMMAR_H
-#define CSSGRAMMAR_H
-EOF
-
-open HPP, "<$fileBase.cpp.h" or open HPP, "<$fileBase.hpp" or die;
-while (<HPP>) {
-    print HEADER;
-}
-close HPP;
-
-print HEADER "#endif\n";
-close HEADER;
-
-unlink("$fileBase.cpp.h");
-unlink("$fileBase.hpp");
-
